Tone generating means for electrical musical instruments



y 1965 B. F. MIESSNER 3,183,296

TONE GENERATING MEANS FOR ELECTRICAL MUSIQAL INSTRUMENTS Filed Nov. 5, 1964 2 Sheets-Sheet 1 y 1, 1965 B. F. MIESSNER 3,183,296

TONE GENERATING MEANS FOR ELECTRICAL MUSICAL INSTRUMENTS Filed Nov. 5, 1964 2 Sheets-$heet 2 United States Patent amazes TONE GENERATING MEANS FOR ELECTRHCAL MUSICAL INSTRUMENTS Benjamin F. Miessner, 680 NE. 1tl5th St, Miami Shores, Fla. Filed Nov. 5, 1964, Ser. No. 499,063 14 Claims. (Cl. 841.15)

This invention relates to electrical musical instruments of the class wherein a plurality of mechanical vibratory elements is combined with means to translate the vibration of such elements into analogous electrical signals, thence into audible music. Examples of instruments of this class are electrical or electronic pianos and organs.

An object of the invention is to provide an instrument of the said class having a novel and improved mechanical vibratory element, hereinafter called a tone generating element or mechanical oscillator, with improved means for translating its vibratory motion into an electrical signal.

Another object is to provide an instrument of the said class having improved means for controlling the relationship between the attack and decay of a tone, by means of electromechanical feedback or regeneration, and the harmonic content of the tone.

Another object is to provide a tone generation means for a musical instrument having improved means for initiating a tone in combination with novel means for controlling independently the decay or sustaining character of the tone.

In the drawings:

FIG. 1- is an isometric view of a portion of a form of the invention;

FIG. 2 is a top view of a portion of a similar form of the invention;

PEG. 3 is a partial sidesectional view of FIG. 2;

FIG. 4 is a partially-schematic top view of another form of the invention, wherein tone generating elements are maintained in vibration by means of air flow;

FIG. 5 is a partially-schematic top view of another form of the invention wherein tone generating elements are energized in part by electrical feedback means;

FIG. 6 is a schematic diagram of an oscillator and demodulator circuit for translating the vibration of such tone generating elecents, via capacitance variations, into electrical signals;

FIG. 7 is an isometric view of an alternative form of tone generating element;

FIG. 8 is an isometric view of another alternative form of tone generating element.

The same reference numerals refer to like elements in all figures.

Referring to FIG. 1, the invention comprises a series of tone generating elements 1 in the general shape of a hairpin or an elongated loop. Said elements are adapted to vibrate in a vertical direction, normal to their own plane, as indicated by arrow 13, and are made of electrically conductive material.

Surrounding the closed end portions 10 of the tone generating elements 1 are magnet pole pieces 3, and inside said end portions 10 are magnet pole pieces 2 of the opposite polarity. Thus the closed end portions 10 of the generating elements are immersed in a radial magnetic field; and when said closed end portions execute a vibratory motion in the vertical direction as indicated by arrow 13, an electrical voltage is induced in the elements 1 and .may be measured orutilized at connections to the ends thereof, as at 11 and 12, FIG. 1.

Situated between the magnet pole pieces 2 and 3 is a magnet 4, which may be of bar shape, magnetized laterally as indicated by the polar markings S, N. A magnet of any other appropriate configuration may be used in harmony with the spirit of the invention. Magnet 4 may be made of a ferrite material, which has high electrical resistivity. In the configuration shown in FIG. 1, magnet 4 provides the magnetomotive force to furnish the magnetic flux in the gaps between pole pieces 2 and 3, parallel to the plane in which lie the generating elements 1. Magnet is located abutting suitable surfaces on the lower portions 2%, 3%, of pole piece members 2, 3.

The open ends of the generating elements 1 are secured to a mounting structure 6, '7, which holds the open ends of elongated loop-shaped elements 1 as at 11, 12, tightly so as to preclude any slight motion which would cause undue dissipation of their vibratory energy. The mounting structure may comprise bars 6, 7 between which the open ends of elements 1 pass, and are clamped by means of screws 15 or other suitable fastening means. The mating surfaces of bars 6 and 7 may be provided with grooves as at 14 to receive tightly the ends of the elements 1. Bars 6 and '7 may be made of electrically insulating material, or alternative means known to the art may be employed to insulate the end portions of vibratory oscillator elements 1.

A base member 5 may be provided, to which the lower portions 29, 3t of pole pieces 2 and 3 are secured, along with bar 6, so that the pole pieces 2, 3 and the tone generating elements 1 are held in a mechanically fixed relationship. Base member 5 is desirably made of non-magnetic material, so as to preclude shunting of the magnetic flux provided by magnet 4.

Each of the tone generating elements 1 may be excited into vibration by being struck by a conventional felt piano hammer 8 or by other known means. One such hammer means is provided for each tone generating element 1. The relationship between the width of the hammer means 8 and the spacing between the two legs of the corresponding tone generating element is such that the hammer means strikes both legs substantially simultaneously, as does a conventional piano hammer when striking two or three piano strings tuned to the same note. The relationship between the width of the hammer means and the spacing between the legs of the tone generating elements 1 is illustrated more particularly in FIG. 2, wherein the hammer means 8 are shown in phantom manner.

Referring to FIG. 2, in the form of the invention wherein the tone generating elements 1 are struck by hammer means 8, the ends of the tone generating means as 11, 12., are all connected in series electrically, and feed the input of an amplifier 9. Amplifier 9 in turn feeds a loudspeaker or equivalent electroacoustic transducer means 16, when any tone generating element 1 is caused to vibrate at its natural frequency, its end portions 10 cut the magnetic flux between the associated pole pieces 2, 3, and an A.-C. electrical voltage is thereby induced in the element 1 and appears between its terminals, as 11 and 12. Said A.-C. electrical voltage is the amplified by amplifier 9, and made audible as a musical tone by electroacoustic trans ducer means 16.

Since relatively pure sinusoidal waves are not satisfactory for musical purposes, the pole pieces 2 and 3 are made relatively thin in vertical extent, so that a substantial portion of the vibratory travel of tone generating elements 1 is in regions of non-uniform magnetic flux, and a tone of relatively high harmonic content is produced. This relationship is illustrated in FIG. 3, a side sectional view, wherein pole pieces 2, 3 are shown relatively thin in the direction of vibratory motion of the element 1, i.e. the direction shown by the arrow 13. Additionally, in order to facilitate the production of evenorder harmonics, which implies an asymetrical waveform in the musical tone, one pole piece, as 3 in FIG. 3, may be offset with respect to the other pole piece 2, so that the plane of maximum magnetic flux is oh set or non- 35 parallel with respect to the plane of symmetry of the vibratory motion of tone generating element 1. Other means may be employed to enhance the even harmonics in the tone, such as mechanicalotfset or bias of the rest position of the tone generating clement ll itself.

Another feature of the invention comprises feedback means applied to the tone generating elements in order to modify the decrement or decay of the musical tones produced, or to produce continuous oscillation of the generating elements 1 to produce organ-like tones. Such feedback means may comprise capacitive pickup elements adapted to generate amplifiable electrical signals in response to the vibratory motion of the tone generating elements I. In FIG. 3, such capacitive pickup elements may, according to the invention, be integral with one of the magnetic pole pieces. In FIG. 3, one of the pole pieces 3 is illustrated as being insulated electrically from the remainder of the structure. Lower portion 36 of pole piece 3 is secured, as by a solder or cement, to the permanent magnet 4, but prevented from electrical contact with base or frame member 5 by means of a strip of insulating material 31. Strip 31 may be omitted if pole piece portion 35% is so mounted as not to contact electrically the base member 5; or member 5 may be made of insulating material. Permanent magnet 4 may be of the known magnetic ceramic or ferrite materials, which are substantially electrical insulators. Pole piece 3 may thus be employed as a capacitive pickup electrode, for purposes of the feedback aforementitoned. The offset location of pole piece 3 shown in FIG. 3 provides means for capacitive pickup of a substantial portion of the fundamental vibration frequency of tone generating element 1, whereas a central location of said pole piece 3 would provide only for the sensing of the even harmonics.

A further feature of the invention is the provision for continuous oscillation of the tone generating elements by means of a flow of air, similarly to the operation of accordion reeds. In FIG. 3, such an air flow may be provided as indicated by the arrow a, the air being restricted to the end portions of the tone generating elements, as bounded by the pole pieces 2, 3, by means of suitable enclosure walls 32, 33, made of any suitable material.

In the form of the invention involving continuous excitation by means of air flow, as indicated at a in FIG. 3, or other known means, and also in FIG. 4, wherein, the tone generating elements 1 are maintained in relatively continuous oscillation, the nature of the invention is additionally set forth. In FIG. 4, the flow of air, indicated by the dotted arrow a, may serve to maintain the tone generating elements or mechanical oscillators 1 in continuous oscillation. To impart to the tones a relatively sharp attack, instead of the passive, gradual attack characteristic of organ-like instruments, there may be provided additionally hammers 8, analogous to the piano hammers 8 illustrated in FIGS. 1, 2, and 3. FIG. 4 shows, in this regard, keying circuitry to utilize these features. Switches 40 are provided in the manner shown in FIG. 4 to connect each tone generating element or oscillator 1 to amplifying means 9, thence to loudspeaker .or equivalent transducing means 16, preferably through a high-ratio input transformer 35. As illustrated in FIG. 4, one side of each U-shaped oscillator element 1 is connected to a common electrical terminal, shown as a ground symbol, and the other side of each such element is selected by means of a switch 4t), which is operated by means of the same manual key (not shown) that operates the hammers 8. Thus, the form of the invention of FIG. 4, comprises tone generating elements or oscillators of the form hereinbefore desecribed, hammer-like means to assist the initiation of mechanical oscillation, and keyoperated switch means to selectively connect the electrical outputs of the mechanical oscillators 1 to an amplifying and electroacoustic transducing system.

FIG. 5 illustrates a form of the invention in which the V mechanical oscillators 1 are maintained in continuous oscillation, or in oscillation of modified decrement, by means of mechanoelectrical feedback. The feedback may be either positive or negative, to effect decrements either lesser or greater, respectively, than those of the oscillators alone. In this embodiment of the invention, the U- shaped oscillator elements 1 may be all connected in series, and an auxiliary electronic amplifying system 45 provided to maintain all the oscillators 1 simultaneously in continuous oscillation. As an adjunct to amplifier 45 there is provided a gain control element fiil to control the amount of feedback in the system and thereby the amplitude and waveform of the musical tones produced. In this embodiment, gain-control potentiometer or equivalent element 39 may be adjusted to provide continuous oscillation of all the tone generating oscillators I simultaneously. The input to system 39, 45, it is observed, is a capacitive pickup means of known type, embodying as its principal element the insulated magnetic pole piece 3, shown best in FIG. 3, although a separate capacitive pickup electrode or electrodes may be provided instead of the integral capacitive-magnetic element 3. The electrical output of amplifier 45 may feed, desirably through an appropriate transformer (no-t shown), the sum of the mechanical oscillators 1 all connected in series, as shown in FIG. 5. Inasmuch as only one of said oscillators has one of its sides connected to ground under these circumstances, it is necessary that key-operated switches 59 be provided of the double-pole type. In practice, it is also most practicable that the outputs of said oscillators ll be fed, via the double-pole switches 59, to audio amplifier 9 through an input transformer 52 of relatively high turns ratio, its primary winding being of only a relatively few turns of wire, appropriate to the low impedance of the tone generating elements or oscillators I.

It is within the purview of the invention that the electromechanical feedback system of FIG. 5 may include nega-- tive feedback as well as positive, i.e. that the auxiliary amplifier means 45 may be made to operate to make the musical tones, generated by means of oscillators 1, decay more rapidly than normal rather than decay more slowly or provide continuous oscillation. This aspect of the invention may be effected by reversing the connections 71, 72 to the input of auxiliary amplifier 45 (FIG. 5), or, alternatively, by reversing its output connections 73, 74. When either of said pairs of connections is reversed, the mechanical forces produced by the flow of amplifier output current into oscillators 1 will be in directions to oppose their motion, and so cause their oscillation to decay more rapidly than it would without the operation of the feedback system comprising elements 3, 39, 45.

Experiment has shown that relatively large electrical signal output voltages are practically obtainable with such oscillators 1 of the kind disclosed, using an appropriate transformer, e.g., 10 volts rms across a high-impedance transformer secondary. The transformer parameters are roughly similar to those of a transformer designed to couple a velocity microphone to the grid of a vacuum tube or to the gate element of a field-effect transistor, both of whose circuitry is well known in the art. The embodiment of FIG. 5 may also have the attack of the tones facilitated by means of mechanical hammers 8, while the decrement or continuance of the tones is modified by means of the electrical feedback'involving magnetic-capacitive pickup electrode 3 and amplifier 45. The invention additionally contemplates that switches 59 may be not merely on-off contact devices, but variableresistance elements (such as carbon piles), as is known in the art, actuated by the pressure or velocity of the keys (not shown) played upon by the musical performer, thus providing a relatively gradual attack of tone, instead of the sudden attack characteristic of electronic organs,

which gives a lifeless, mechanical produced.

It is additionally contemplated that means may be provided to individually adjust the magnitude of the feedback current to each of the tone generating elements 1, FIG. 5, or to groups of said elements, in order to set the feedback ratios individually to provide appropriate magnitudes of oscillation amplitude to each element. Such means may comprise individual variable shunt resistors or potentiometers as is known in the art.

FIG. 6 illustrates schematically the circuit of an oscillator and demodulator suitable for sensing the motion of the vibrating tone generator elements 1, through the agency of a capacitive pickup electrode such as the pole piece 3. In FIG. 6, said pole piece 3 is shown together with tone generating elements 1, which are connected in series, with one terminal of one element grounded at point 66. Thus the set of elements 1 constitutes, in operation, one side of an electrical capacitance which is substantially grounded, because of the relatively low resistance of said elements. When one or more of said elements vibrates, the motion provides a cyclic variation in this capacitance, which may be translated into suitable Variations in electrical voltage for the purpose of feeding to an amplifier such as 9 and to speaker means 16. The capacitancetranslating circuit shown comprises a transistor 65 and a transformer having three windings 47, 48, 49. Winding 47 together with capacitors 56, 51 constitute a tuned circuit, resonant at a carrier frequency relatively high compared to the frequencies of the tone generating elements, e.g. 100 kilocycles, 1 megacycle, or more. Feedback connection 70 to the emitter of transistor 65, plus the conventional biasing resistors shown, operate in known manner to generate continuous electrical oscillations at the resonant frequency of the tuned circuit 47, 5%, 51. The additional transformer winding 4? has a center-tap 60; one side 61 of said winding is connected to the capacitive pickup electrode 3, and the other side 62 to an adjustable balancing capacitor 58. Balancing capacitor 53 is normally adjusted to approximately equal the capacitance from electrode or pole piece 3 to ground. Thus there is relatively little or no carrier voltage between center-tap 60 and ground. The carrier voltage variation may then be demodulated by means of a phase-sensitive demodulator or detector comprising diodes 52, 53, switched from winding 48; and the demodulated output will appear across terminals 56, 57, connected across a suitable load resistor 55 and carrier bypass capacitor 54. Said demodulated output will constitute a voltage replica of the capacitance variations between grounded generator elements and capacitance pickup electrode 3. Power is supplied by any suitable supply 46.

The foregoing detailed description of the circuit is provided in order to make clearer the nature of the invention, and not to restrict the invention to this patricular type of circuitry. Any of the known capacitance translating circuits may be employed, although the one shown is particularly eifective and economical, and requires no electrostatic shielding as does the conventional type of circuit used with capacitor microphones.

FIGS. 7 and 8 illustrate alternative forms of the tonegenerating elements or mechanical oscillators 1. FIG. 7 shows such an element 63, which may be struck out of sheet metal. It comprises elongated legs 41 and an end portion 42 which is bent at an angle to the plane of the legs 41. End portion 42 may serve as a capacitance elecquality to the music .trode, adjacent a stationary capacitance pickup electrode such as 3 (FIGS. 1-6), and having a relatively large area.

FIG. 8 shows a form of mechanical oscillator 64 which may be similarly made by striking out of sheet metal, wherein legs 43 converge at a relatively small angle toward end portion 44. End portion &4 may serve as a capacitance electrode of relatively large area, similarly to end portion 42 of FIG. 7, thereby permitting an increased magnitude of signal to the capacitance translating circuitry. The angular divergence of leg portions 43 increases the stifiness of the element in its own plane and in torsion, thus reducing the amplitudes of vibration in those modes which do not contribute to the musical tone output.

I claim:

1. Apparatus for generating musical tones comprising a mechanical oscillator in theform' of an elongated electrically-conductive loop having a free closed end portion and two fixed open end portions, and disposed substantially in oneplane,

a magnet structure defining a radial magnetic field whose lines of force extend in and parallel to said plane and intersect said closed end portion,

means to excite said oscillator into vibratory oscillation at its natural frequency in a direction substantially normal to said plane,

electroacoustic transducing means,

and an electrical signal path from said open end portions to said transducing means.

2. In an electrical musical instrument, an elongated conductive fixed-free vibratory loop having fixed open ends, and

a magnet structure providing a radial magnetic field intersecting said loop,

whereby vibration of said loop generates an electrical voltage between its open ends.

3. The invention according to claim 2, further comprising means to excite mechanical oscillation of said loop, and

pickup means and auxiliary amplifier means to modify the decrement of said oscillation,

the output of said auxiliary amplifier means furnishing signal current to the terminals of said loop.

4. The invention according to claim 3, wherein said auxiliary amplifier means is connected to increase the decrement of said oscillation.

5. The invention according to claim 3, wherein said auxiliary amplifier means is connected to decrease the decrement of said oscillation.

6. The invention according to claim 2, further comprising key-actuated hammer means disposed to strike both sides of said loop substantially simultaneously to excite it into vibratio 7. The invention according to claim 2, further comprising key-actuated hammer means to excite said loop into vibration at its natural frequency,

said magnet structure including a magnetic, conductive,

electricaHy-insulated pole piece adapted to serve addi-tionally as a capacitive position pickup electrode.

8. In an electrical musical instrument, an elongated conductive fixed-free vibratory loop having its open ends fixed and adapted to vibrate in a direction perpendicular to its own plane,

a magnet structure providing a substantially radial magnetic field intersecting a portion of said loop, vibration of said loop generating an alternating electrical voltage available at said open ends,

percussive means to excite said loop into vibration at its lowest natural frequency,

pickup means to translate vibratory motion of said loop into an electrical signal,

auxiliary amplifier means having an output connected to drive said loop and fed from said electrical signal, and

a main amplifier fed from said alternating electrical voltage and feeding an electroacoustic transducer.

9. In an electrical musical instrument, means according to claim 5, wherein said pickup means is a magnetic pole piece integral with said magnet structure.

10. In an electrical musical instrument, means according to claim 5, wherein said magnet structure cornprises a magnetic pole piece operative as a capacitive magnetic relation to said pole piece.

11. In an electrical musical instrument, an elongated conductive fixed-free vibratory loop having its open ends fixed and adapted to vibrate in a direction perpendicular to its own plane,

a magnet structure providing a substantially radial magnetic field intersecting an end portion of said loop, vibration of said loop generating an alternating electrical voltage available at said open ends,

pickup means adapted to translate vibratory motion of said loop into an electrical signal,

auxiliary amplifier means fed from said electrical signal and feeding said open ends of said loop to produce regenerative continuous oscillation of said loop,

a main amplifier and electroacoustic transducer fed from said alternating electrical Voltage to produce an audible musical tone, and

gain control means connected in the amplification path of said auxiliary amplifier to control the magnitude of said regenerative continuous oscillation. 12. The invention according to claim 8, further comprising exciting means to impulsively excite vibratory oscillation of said loop.

13. An electrical musical instrument comprising a plurality of fixed-free vibratory loops', ea-ch lying sub stantially in a plane and adapted to vibrate at its natural frequency in a direction substantially normal to said plane, and

a magnet structure having a plurality of substantially radial magnetic gaps providing lines of force intersecting a portion of each of said loops to generate an electrical alternating voltage in said loops in response to their vibration,

at least some of said loops having two substantially parallel leg portions of rectilinear cross-section and an end portion bent at right angles to said leg portion,

and means to translate said alternating voltage into audible sound.

14. An electrical musical instrument according to claim 10, wherein at least some of said loops have leg portions disposed at an acute angle to each other and an end portion disposed substantially at right angles to said leg portions, each of said portions having substantially the same thickness and a substantially rectangular crosssection.

No references cited.

ARTHUR GAUSS, Primary Examiner. 

1. APPARATUS FOR GENERATING MUSICAL TONES COMPRISING A MECHANICAL OSCILLATOR IN THE FORM OF AN ELONGATED ELECTRICALLY-CONDUCTIVE LOOP HAVING A FREE CLOSED END PORTION AND TWO FIXED OPEN END PORTIONS, AND DISPOSED SUBSTANTIALLY IN ONE PLANE, A MAGNET STRUCTURE DEFINING A RADIAL MAGNETIC FIELD WHOSE LINES OF FORCE EXTEND IN AND PARALLEL TO SAID PLANE AND INTERSECT SAID CLOSED END PORTION, MEANS TO EXCITE SAID OSCILLATOR INTO VIBRATORY OSCILLATION AT ITS NATURAL FREQUENCY IN A DIRECTION SUBSTANTIALLY NORMAL TO SAID PLANE, ELECTROACOUSTIC TRANSDUCING MEANS, AND AN ELECTRICAL SIGNAL PATH FROM SAID OPEN END PORTIONS TO SAID TRANSDUCING MEANS. 